CN-122017451-A - Line protection fault identification method and system

CN122017451ACN 122017451 ACN122017451 ACN 122017451ACN-122017451-A

Abstract

The invention relates to the technical field of fault identification, in particular to a line protection fault identification method and system, which can be used for respectively sampling currents at two sides of a target line in real time in the target line to respectively obtain sampling current sequences at the two sides, integrating sampling values of the sampling current sequences obtained by sampling to obtain corresponding integrated current sequences, calculating three-phase current correlation coefficients of the integrated current sequences at two sides by using a waveform similarity algorithm, wherein if the current correlation coefficient of a certain phase meets a protection criterion, the phase is a fault phase, otherwise, the phase is a non-fault phase. It can be understood that the technical scheme removes the influence of high-frequency components by carrying out short-time integral sampling on the current, is not constrained by small amplitude of fault current of a new energy scene, has strong adaptability to excessive resistance, has better high-frequency tolerance than a common waveform similarity algorithm, and can prevent malfunction of faults outside a line protection area in a scene with larger high-frequency content of a new energy sent-out line.

Inventors

XU SHOUDONG
ZHANG LI
XI XINZE
SHI HENGCHU
JIN FAJU
CHEN YONG
LU JIA
HU YUELIN
FENG YANQI

Assignees

云南电网有限责任公司电力科学研究院

Dates

Publication Date: 20260512
Application Date: 20260104

Claims (10)

1. A line protection fault identification method, comprising: In a target line, respectively sampling currents of a first side and a second side of the target line in real time to obtain a first side sampling current sequence and a second side sampling current sequence; Respectively integrating sampling values of the first side sampling current sequence and the second side sampling current sequence to obtain a first side integration current sequence and a second side integration current sequence; Calculating three-phase current correlation coefficients of the first side integral current sequence and the second side integral current sequence by utilizing a waveform similarity algorithm; If the current correlation coefficient of a certain phase meets the protection criterion, the phase is a fault phase, otherwise, the phase is a non-fault phase.
2. The line protection fault identification method of claim 1, wherein integrating the sampled values of the first side sampled current sequence and the second side sampled current sequence, respectively, comprises: And respectively integrating the sampling values of the first side sampling current sequence and the second side sampling current sequence by using a quarter-cycle sampling time window.
3. The line protection fault identification method according to claim 2, wherein integrating the sampled values of the first side sampled current sequence and the second side sampled current sequence, respectively, comprises: And respectively integrating sampling values of the first side sampling current sequence and the second side sampling current sequence by the following formula: Wherein k is the current sampling point, X (k) is the sampling value corresponding to the k point, X' (k) is the value after k point integration, i is the hysteresis sequence number relative to the current sampling point k in the integration window, N Int is the number of integration points; The integral data window is 1/4 fundamental wave, and the integral point number is calculated by the following formula: Where N b is the number of sampling points for one cycle, f s is the sampling frequency, and f b is the fundamental frequency.
4. The line protection fault identification method of claim 1, wherein calculating three-phase current correlation coefficients of the first side integrated current sequence and the second side integrated current sequence using a waveform similarity algorithm comprises: The three-phase current correlation coefficients of the first side integrated current sequence and the second side integrated current sequence are calculated by the following formula: x={x 1 ,x 2 ,…,x n } y={y 1 ,y 2 ,…,y n } where r (x, y) is the correlation degree of the variable x and the variable y, and n is the sampling point number.
5. The line protection fault identification method of claim 1, wherein the real-time sampling of the current on the first side and the second side of the target line further comprises: the sampling frequency is less than 1.5kHz.
6. The line protection fault identification method according to claim 1, wherein the protection criterion is that when the current correlation coefficient of the same-name phases on both sides is between-0.9 and +1 at the same time, the phase is a fault phase.
7. The line protection fault identification method as claimed in claim 1, wherein, The target line is a new energy station sending line, the first side is a station side, and the second side is a system side.
8. The line protection fault identification method of claim 1, further comprising: after the fault phase is identified, outputting an alarm of the fault in the area of the circuit, and simultaneously protecting the fault phase; If the three-phase current correlation coefficients do not meet the protection criterion, judging that the three-phase current correlation coefficients are out of zone faults and protecting and resetting.
9. A line protection fault identification system, comprising: the first microcomputer protection device is arranged on the first side of the target line and is used for sampling the current of the first side of the target line in real time to obtain a first side sampling current sequence; the second microcomputer protection device is arranged on the second side of the target line and is used for sampling the current of the second side of the target line in real time to obtain a second side sampling current sequence; The system comprises a calculation and identification module, a waveform similarity algorithm, a fault phase and a non-fault phase, wherein the calculation and identification module is used for respectively carrying out sampling value integration on a first side sampling current sequence and a second side sampling current sequence to obtain a first side integration current sequence and a second side integration current sequence, calculating three-phase current correlation coefficients of the first side integration current sequence and the second side integration current sequence by the waveform similarity algorithm, and if the current correlation coefficient of a certain phase meets a protection criterion, the phase is the fault phase, otherwise, the phase is the non-fault phase.
10. The line protection fault recognition system according to claim 9, wherein the first microcomputer protection device and the second microcomputer protection device are each provided with a low-pass filter for filtering out high-frequency components having a frequency equal to or higher than a sampling frequency.

Description

Line protection fault identification method and system Technical Field The invention relates to the technical field of fault identification, in particular to a line protection fault identification method and system. Background The method is influenced by the fault characteristics of a new energy power supply, the amplitude of a new energy output fault current is limited, the phase angle is controlled, only positive sequence current is output under a low-pass control strategy for inhibiting negative sequence current, zero sequence and negative sequence current are not generated, the reliability of traditional current protection and differential protection is affected to a certain extent, and aiming at the background of a double-high power grid connected with a power grid, the power flow of the power grid flows bidirectionally and has a large change range, the topological structure is complex, the reverse current of the fault of an adjacent line is easy to cause overcurrent protection misoperation, and the power frequency and transient analysis method based on the power supply of the synchronous generator is not applicable any more. The waveform similarity algorithm is an algorithm for measuring the similarity degree between different waveforms or sequences, and has obvious advantages in the aspect of distinguishing different state waveforms because the waveform similarity algorithm is not constrained by waveform amplitude values, so that domestic and foreign specialists conduct a great deal of research in line protection of a power system by using the waveform similarity algorithm, and a method for distinguishing faults by using transient waveform similarity becomes an effective means. However, most of the existing waveform similarity algorithms depend on a low-pass filter additionally arranged in protection to reduce the influence of new energy high-frequency quantity, or wavelet transformation is needed to perform data preprocessing, so that the calculated quantity is large, and the high-frequency content of the new energy is considered to be large, so that misoperation is easy to occur when the existing algorithms face faults outside the area. Disclosure of Invention In view of the above, the present invention is to provide a line protection fault recognition method and system, so as to solve the problem of malfunction of the out-of-zone fault under the high frequency influence of new energy when the waveform similarity algorithm in the prior art faces the out-of-zone fault. According to a first aspect of an embodiment of the present invention, there is provided a line protection fault identification method, including: In a target line, respectively sampling currents of a first side and a second side of the target line in real time to obtain a first side sampling current sequence and a second side sampling current sequence; Respectively integrating sampling values of the first side sampling current sequence and the second side sampling current sequence to obtain a first side integration current sequence and a second side integration current sequence; Calculating three-phase current correlation coefficients of the first side integral current sequence and the second side integral current sequence by utilizing a waveform similarity algorithm; If the current correlation coefficient of a certain phase meets the protection criterion, the phase is a fault phase, otherwise, the phase is a non-fault phase. Preferably, the integrating of the sampled values of the first side sampled current sequence and the second side sampled current sequence respectively includes: And respectively integrating the sampling values of the first side sampling current sequence and the second side sampling current sequence by using a quarter-cycle sampling time window. Preferably, the integrating of the sampled values of the first side sampled current sequence and the second side sampled current sequence respectively includes: And respectively integrating sampling values of the first side sampling current sequence and the second side sampling current sequence by the following formula: Wherein k is the current sampling point, X (k) is the sampling value corresponding to the k point, X' (k) is the value after k point integration, i is the hysteresis sequence number relative to the current sampling point k in the integration window, N Int is the number of integration points; The integral data window is 1/4 fundamental wave, and the integral point number is calculated by the following formula: Where N b is the number of sampling points for one cycle, f s is the sampling frequency, and f b is the fundamental frequency. Preferably, calculating the three-phase current correlation coefficients of the first side integrated current sequence and the second side integrated current sequence using a waveform similarity algorithm includes: The three-phase current correlation coefficients of the first side integrated current sequence and the second sid